Chapter 2 part II array and structure.pptx

1
Chapter 2
Array and Structure
Part II
Structure
Computer Programming II (Seng-2021)

3
Structure
 structures are used to group related components of different types
 Components of the such a structures are called fields
 A structure is a collection of variables of different data types under a single name.
 A structure is a user-defined data type in C/C++, store Heterogeneous data type,
 Recall that elements of arrays must all be of the same type
 In some situations, we wish to group elements of different types
employee R. Jones 123 Elm 6/12/55 $14.75
scores : 85 79 92 57 68 80 . . .

4
Cont.
 structures are used to group related components of different types
 Components of the such a structures are called fields
 In C++

called a struct
 fields called members
 C++ struct

structured data type

fixed number of components

elements accessed by name, not by index

components may be of different types
struct PartStruct{
char descrip [31], part_num [11];
float unit_price;
int qty; };

5
Structure Declaration
 Structure declaration creates a user defined data type that can hold different types of
logically related data items.

Eg: A structure defined to hold book database.
struct book
{
char name[20];
char author[15];
int pages;
float price;
};
 structkeyword used to declare a structure. Tells the compiler what follows is a data type definition.
 What is enclosed within the structure is the body of the structure.
 Body of the structure contains the elements of the structure, where each element declaration ends up with a
semicolon.
 Structure definition is a single statement and is terminated within a semicolon.

6
Cont.
General syntax: struct <structure-name>
{
data-type member 1;
data-type member 2;
…………………
data-type member n;
};
 Here structure –name is called the structure tag and elements are called the members.
 Structure declaration does not create any structure variables.
 It does not tell the compiler to reserve any space in memory. It just defines the form of the structure.
Declaration of Structure variables:
1. Structure variables can be declared as: Structure name var1,var2,…..var n;
Eg: struct book
{
char name[20];
char author[15];
int pages;
float price;
};
book mybook1,mybook2; Two structure variables of type book is
Eg: struct book
{
char name[20];
char author[15];
int pages;
float price;
}mybook1, mybook2;
1. It’s possible to combine the declaration of the structure
type and the variable declaration in one statement.

7
Memory allocation for the structure variables:
 Space in memory is set aside for structure variables when they are declared.
 It makes space available to hold all the elements of the structure.
 Also structure elements are placed in contiguous memory locations.
Eg: struct
{
char name[20];
char author[15];
int pages;
float price;
}mybook1;
Here 41 bytes is reserved for the variable mybook1. (20 bytes
for name, 15 bytes for author,2 bytes for pages and 4 for
price).
Initializing Structure Data
– Giving values to the members of the structure at the time of the declaration of structure variables.
– Initial values are enclosed in braces separated by commas in the order of the elements defined in the structure
declaration.
– The initialization statement must end with a semicolon.

8
Cont.
Eg: struct book
{
char name[20];
char author[15];
int pages;
float price;
}mybook1={“Let us C++”,Tom,760,320.75};
book mybook2={“Let us C+
+”,Tom,760,320.75};
Accessing Structure Elements
The structure elements can be accessed by the use of the variables of the structure and the dot operator (member operator).
For e.g:
mybook1.name;
mybook1.author;
Note:
 A structure may be local (to a function) if defined within a function. That is, no function other than the
one, which defines it, can access it.
 A structure may be global (to all functions within the program) if defined outside all functions. That is,
any functions can access it.

9
Cont.
Example 1:
//Using a structure to deal with student information
#include<iostream.h>
void main()
{
struct student
{ char name[10];
int rollno;
float mark[5];
}stud1;
cout<<"Enter the name:";
cin>>stud1.name;
cout<<"Enter the rollno:";
cin>>stud1.rollno;
for(int i=0;i<3;i++)
{
cout<<"Enter the mark for subject["<<i<<"]";
cin>>stud1.mark[i];
}
}

10
Structure and Array
 Arrays and structure can be combined together to form complex data objects.
 There may be structures within an array; also there may be array as elements of a
structure.
Arrays of Structures:

Having structures as elements of array is. arrays of structure
 For example consider the structure student in Example 1. To store the details of 100 students we
need to create an array of structure ‘student’.

To declare an array of structure, define a structure, then declare an array variable of that type.

E.g: student stud[100];

To access specific structure, index the structure name. E.g: stud[1].name;

11
Cont.
Example 2: //Array of student structure
void main()
{ struct student
{ char name[10];
int rollno;
float mark[5];
}stud[10];
int n,i,j;
cout<<"Enter the number of students;";
cin>>n;
for(i=0;i<n;i++)
{ cout<<"Enter the name:";
cin>>stud[i].name;
cin>>stud[i].rollno;
for(j=0;j<3;j++)
{ cout<<"Enter the mark for
subject["<<j<<"]"; cin>>stud[i].mark[j];
}
}
cout<<"nName:tRollnotMark1tMark2tMark3n";
for(i=0;i<n;i++)
{ cout<<"n"<<stud[i].name<<"
t"<<stud[i].rollno<<"t";
for(j=0;j<3;j++)
{
cout<<stud[i].mark[j]<<"t";
}}}

12
Nested Structures:
Structures as members of another structure.
Eg: struct Address
{
int hno;
char city[10];
};
struct student
{
char name[10];
Address add;
int rollno;
float mark[5];
}stud;
Members of the nested structure is referenced from the outermost to innermost with the help of dot
operators.
stud.add.hno=10;
Assignment of a complete structure

One structure variable can be assigned to another only when they are of the same structure type.

Only assignment is possible for two similar structures. Other operations such as comparisons are not
possible.

13
Passing & Returning Structures in Functions
 A function is a named unit of a group of program statements which can be invoked from other parts of
the program.
 If structure and structure variable is global then it is available to all functions in the program and so
not necessary to pass as arguments.
 If a structure is local to a function and if its value is needed in other functions,
 we can pass the structure as arguments to the function.
 It can be achieved in 2 ways:
1) by passing individual structure elements.
(2) by passing entire structure.
 For e.g: function1(stud1.name,stud1.rollno);
 here function1 is called by passing values of individual structure elements of structure student.
 Now, If the values of structure elements should not be altered by the function, then structure elements
are passed by value and if the values of structure elements can be altered by the function, then structure
elements are passed by reference.
 Array elements will automatically be passed by reference as the arrays cannot be passed by value.
 Passing entire structure makes the most sense when the structure is relatively compact. Entire
structure can be passed by value or reference.

14
Call by reference
Exampe: Call by reference
struct student
{
char name[10];
int rollno;
float mark[5];
};
void read(student *stud)
{
int i;
cin>>(*stud).name;
cin>>(*stud).rollno;
for(i=0;i<3;i++)
{
cin>>(*stud).mark[i];
}
}
void display(student *stud)
{
cout<<"Display...........n";
cout<<"n"<<(*stud).name<<"
t"<<(*stud).rollno<<"t";
for(int j=0;j<3;j++)
{
cout<<(*stud).mark[j]<<"t";
}}
void main()
{
student st;
read(&st);
display(&st);
}

15
The arrow operator (->)
 This is a dereference operator that is used exclusively with pointers to objects with
members.
 This operator serves to access a member of an object to which we have a reference.
 In the example we used: (*stud).name which is equivalent to stud->name;
 Both expressions (*stud).name and stud->name;
 are valid and both mean that we are evaluating the member name of the structure pointed by a
pointer called stud.
 Possible combinations of pointers and structure members:
Expression What is evaluated Equivalent
a.b Member b of object a
a->b Member b of object pointed by a (*a).b
*a.b Value pointed by member b of object a *(a.b)

16
Function Returning Structures
 If a function read() wants to return a structure of type student its declaration is as
student read().
 If the return value of the function read() is being assigned to a variable, then that
variable must be a structure variable of type student. student std=read();
Example: Call by value & function returning structure
struct student
{
char name[10];
int rollno;
float mark[5];
};
student read(student stud)
{
int i;
cout<<"Enter the name:"; cin>>stud.name;
cin>>stud.rollno;
for(i=0;i<3;i++)

17
Cont.
cin>>stud.mark[i];
}
return stud;
}
void display(student stud)
{
cout<<"Display...........n";
cout<<"n"<<stud.name<<"
t"<<stud.rollno<<"t";
{
cout<<stud.mark[j]<<"t";
}
}
void main()
{
student st;
st=read(st);
display(st);
}

18
Cont.
Example: Passing Array of Structure in function
struct student
{
char name[10];
int rollno;
float mark[5];
};
int read(student stud[])
{int i,n,j;
cout<<"Enter the total number of students:";
cin>>n;
for(i=0;i<n;i++)
{
cin>>stud[i].name;
cin>>stud[i].rollno;
for(j=0;j<3;j++)
{
cout<<"Enter the mark for
subject["<<i<<"]";
cin>>stud[i].mark[j];
}
}return n;
void display(student stud[],int n)
{ for(int i=0;i<n;i++)
{ cout<<"n"<<stud[i].name<<"
t"<<stud[i].rollno<<"t";
{ cout<<stud[i].mark[j]<<"
t";
}}}
void main()
{
student st[10]; int s;
s=read(st);
display(st,s);
}

19
Work sheet
Suppose you are designing a program to store information about employees in a company. You decide to
use a struct to represent the employee's data. The struct definition is as follows:
1) Declare a variable named "emp1" of type "Employee".
2) Initialize the "emp1" variable with the following values:
employeeID: 1001
name: "John Smith"
age: 32
salary: 50000.0
3) Declare another variable named "emp2" of type "Employee".
4) Prompt the user to enter values for the "emp2" variable, including the employeeID, name, age, and
salary.
5) Write a function named "printEmployee" that takes an "Employee" object as a parameter and prints the
employee's information in the following format:
6) Example output: "Employee ID: 1001, Name: John Smith, Age: 32, Salary: $50000.00"
7) Call the "printEmployee" function twice, once for each of the "emp1" and "emp2" variables.

Chapter 2 part II array and structure.pptx

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Chapter 2 part II array and structure.pptx